Applies temporary host optimisations (CPU governor, I/O and process priority) for the game's lifetime, then restores them on exit. GameMode runs the game, so %command% is what it runs.
Proton-Deck
Feral GameModeAdded Jun 29, 2026Last checked Sep 12, 2026
Safe
mangohud %command%Copy
Show the MangoHud performance overlay (Linux)
Effect
Draws FPS, frame timing and CPU/GPU load over Vulkan and OpenGL games. MangoHud runs the game, so %command% is what it runs.
Proton-Deck
MangoHudAdded Jun 29, 2026Last checked Sep 12, 2026
Safe
-ResX=1920Copy
Set the window width in pixels (Unreal Engine games)
Effect
Takes its value with = and no space. Epic pairs it with -ResY and -windowed.
Example
-windowed -ResX=1920 -ResY=1080
Display
Unreal EngineAdded Aug 11, 2026Last checked Sep 9, 2026
Safe
-ResY=1080Copy
Set the window height in pixels (Unreal Engine games)
Effect
Takes its value with = and no space. Epic pairs it with -ResX and -windowed.
Example
-windowed -ResX=1920 -ResY=1080
Display
Unreal EngineAdded Aug 11, 2026Last checked Sep 9, 2026
Safe
-windowedCopy
Run in windowed mode (Unreal Engine and Source games)
Effect
Unreal documents pairing it with an explicit resolution. In Source -window, -sw and -startwindowed are the same option.
The way to fix this is by setting the next launch parameters to the game: You can do this by right clicking the game on the steam library, properties, set launch options
On the General tab, find the Launch Options field.
Type or paste the option (e.g. -windowed) into the field. To use several at once, separate them with spaces (e.g. -windowed -novid).
Close Properties. Steam saves automatically, and the option applies next time you launch the game.
To remove one, reopen the same field and delete the text. Options are game-specific; an option that helps one game may do nothing (or misbehave) in another.
Worth knowing: a launch option can break a game's rendering, reset local settings, or trip anti-cheat in multiplayer. Read the description first, add one at a time, and treat anything rated above Safe as a deliberate experiment.
